A graduate student will be directly involved with the project. A number of students will potentially be involved in various stages of the study.

SCEC Priorities

5, 4, 2

SCEC Groups

Seismology, Geodesy, SDOT

Report Due Date

03/15/2014

Date Report Submitted

N/A

Project Abstract

A mini seismic array was installed near Cholame and Parkfield to record a wide spectrum of seismic activity in the San Andreas Fault (SAF). The array was designed and placed in a way such that it can scan both the Cholame section that produces prolific tremor activity and the Parkfield patch that breaks repeatedly producing M6 earthquakes. We have recorded about one year of continuous high-quality broadband data. Preliminary analyses of the first one-month of the array data reveal about 5 times more duration of tremor activity compared to a conventional method using the existing network [Nadeau and Guilhem, 2009]. I observed 2-3 patches of tremor activity in the SAF. They are located either under Cholame or near Parkfield. More detail and complete analyses of the data may reveal new details of tremor activity providing new insights into the SAF dynamics in this locale.

Intellectual Merit

This study collected high-resolution broadband seismic array data at San Andreas Fault (SAF) near Parkfield and Cholame. This unique dataset can be used to track seismic activity in San Andreas Fault in great detail, and image a broad spectrum of seismic activity including tremor and regular earthquakes. This is extremely important for this part of the SAF as it marks the transition between locked and creeping parts of the fault and produce damaging M6 earthquakes repeatedly. This data may give a better understanding of fault rheology at depth and how earthquakes interact across a broad spectrum.

Broader Impacts

This study aims to better understand the dynamics of SAF near Parkfield that repeatedly produce damaging earthquakes. It has significant implications on the seismic hazard for this part of SAF. As a part of this study, several undergraduate students are given the opportunity to involve in the fieldwork, and received training to install seismograph stations. It supported a graduate student, and helped a starting Assistant Professor to build a quality research program.

Exemplary Figure

Figure 2: Tremor detection in minutes per day using only the seismic array (left) and the existing seismic network (right). For the array detection, a beam-backprojection technique is used [Ghosh et al., 2009; 2012]. For detection by the standard seismic network, an envelope cross-correlation technique is used [Nadeau and Guilhem, 2009].